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MissingDataRules

is an option for SemanticImport and related functions that specifies what should be considered "missing" and what to replace it with.

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MissingDataRules

MissingDataRules

is an option for SemanticImport and related functions that specifies what should be considered "missing" and what to replace it with.

Details

  • MissingDataRules->{s1->val1,s2->val2,…} specifies that whenever an element has the form of a string or string pattern si, it should be replaced in the output by a Missing incorporating vali.
  • MissingDataRules-><|name1->{s1->val1,…},name2->…,…|> specifies replacements to use in columns with names namei.
  • MissingDataRules->{{s1->val1,…},…} specifies replacements to use in successive columns.
  • If vali is of the form Missing[…], it is used directly.
  • MissingDataRules->Automatic uses heuristics to determine which elements should be considered missing.

Examples

Basic Examples  (5)

Specify how to handle missing data:

Wolfram Language code: exampleText = "a a a aa aa a aa aa"
Wolfram Language code: Grid[SemanticImportString[exampleText, Automatic, "Rows", MissingDataRules -> {"a" -> Missing["b"]}]]

Match missing data by pattern:

Wolfram Language code: exampleText = "a a a aa aa a aa aa"
Wolfram Language code: Grid[SemanticImportString[exampleText, Automatic, "Rows", MissingDataRules -> {("a" ~~ __) -> Missing["b"]}]]

Handle missing data differently in each column:

Wolfram Language code: exampleText = "a a a aa aa a aa aa"
Wolfram Language code: Grid[SemanticImportString[exampleText, Automatic, "Rows", MissingDataRules -> {{("a" ~~ __) -> Missing["b"]}, {"a" -> Missing["c"]}}]]

Handle missing data in the second column only:

Wolfram Language code: exampleText = "a a a aa aa a aa aa"
Wolfram Language code: Grid[SemanticImportString[exampleText, Automatic, "Rows", MissingDataRules -> {{}, {"a" -> Missing["b"]}}]]

Specify how to handle missing data by column name:

Wolfram Language code: exampleText = "c1 c2 a a a aa aa a aa aa"
Wolfram Language code: Grid[SemanticImportString[exampleText, Automatic, "Rows", MissingDataRules -> <|"c2" -> {("a" ~~ __) -> Missing["b"]}, "c1" -> {"aa" -> Missing["c"], "a" -> Missing["d"]}|>]]
Wolfram Research (2014), MissingDataRules, Wolfram Language function, https://reference.wolfram.com/language/ref/MissingDataRules.html.

Text

Wolfram Research (2014), MissingDataRules, Wolfram Language function, https://reference.wolfram.com/language/ref/MissingDataRules.html.

CMS

Wolfram Language. 2014. "MissingDataRules." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/MissingDataRules.html.

APA

Wolfram Language. (2014). MissingDataRules. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/MissingDataRules.html

BibTeX

@misc{reference.wolfram_2026_missingdatarules, author="Wolfram Research", title="{MissingDataRules}", year="2014", howpublished="\url{https://reference.wolfram.com/language/ref/MissingDataRules.html}", note=[Accessed: 12-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_missingdatarules, organization={Wolfram Research}, title={MissingDataRules}, year={2014}, url={https://reference.wolfram.com/language/ref/MissingDataRules.html}, note=[Accessed: 12-June-2026]}